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Slide Rules

Index by Makers & Retailers

Hundreds of companies around the world were involved in the production of slide rules from the 18th to the 20th centuries. Click on one of the names below to see the objects in this collection that were associated with that firm.

This 20-inch mahogany linear slide rule is coated on the front and back with white celluloid; the edges are bare. The scales are labeled on the right end of each side. On both sides, the top of the base has an A scale, and the bottom of the base has a D scale. On one side, the slide has B and C scales; on the other, the slide has BI and CI scales. The rule has two indicators: the original brass double-chisel style indicator, and the frameless glass with plastic edges that Keuffel & Esser adopted in 1915. According to the donor, the second indicator was acquired some years after the original slide rule.

The bottom of the base on one side and the chisel indicator on the other side are both marked: KEUFFEL & ESSER Co. NEW-YORK. The bottom of the base is also engraved: CHAS. C. BRUSH 1901. The symbol for pi has also been scratched on the D scale on that side. On the other side, the bottom of the base is marked: PAT. OCT. 6. 1891. One edge of the frameless indicator is marked: K&E.CO.N.Y. (/) PAT.8.17.15. For information on these patents, see MA*318477 and MA*318475.

The cardboard case is covered with brown morocco leather. It is marked: KEUFFEL & ESSER CO. (/) DUPLEX (/) SLIDE RULE. See the similar case for MA*326613.

According to the donor, the instrument was used by his father, Charles C. Brush (1880–1968), who graduated from high school in Philadelphia in 1898 and subsequently studied at the Franklin Institute. He received a certificate from the School of Naval Architecture there in 1904. The model 4078 is only listed in Keuffel & Esser catalogues for 1901 and 1903, priced at $16.50. The catalog evidence and the date on the slide rule make it reasonable to suppose that Brush acquired the slide rule in the course of his studies. Charles C. Brush was then associated with the Bureau of Lighthouses from 1917 to 1939. When the Lighthouse Service ended in 1939, he served as a marine engineer in the engineering department of the U.S. Coast Guard until his retirement in 1944.

This ten-inch aluminum linear slide rule has a yellow ("eye saver") coating and a nylon indicator. The front of the base has L, DF, D, and DI scales, with B, ST, T, S, and C scales on the slide. The left end of the slide is marked: MODEL (/) N1010-ES (/) TRIG. The right end of the slide has the style of Pickett logo used between 1958 and 1962, with MADE IN U.S.A. printed below the logo.

A black leather case is lined in pink plastic. The triangular Pickett logo stamped in gold below the slot for the case's flap is wearing away. The back of the case has a metal ring for attaching to a belt. Inside the flap is the name and address of David D. Goldberg, who was apparently the first owner of the instrument. It then passed to Janis Popowicz, who donated the rule to the Smithsonian while she was technician in the Division of Mathematics from September 1977 to April 1978. She used it as a high school physics student.

As is the case for many Pickett slide rules (e.g., 1991.0445.02), the dating for this instrument is ambiguous. The copyright date, logo, shape of the posts, and location of the grooves (on the slide instead of on the base) are all consistent with a date between 1958 and 1962. However, Pickett & Eckel only moved to Santa Barbara, Calif., and took the new name of Pickett Industries in 1964. The logo changed in 1962 and again in 1964. See the company history with 1998.0119.02.

Computing devices have been manufactured for military purposes since at least the early 17th century. Around the end of World War II, the Chicago firm of Felsenthal designed an instrument like a slide rule for aiming a variety of howitzers, or short cannons, used by the U.S. Army, including the 155 mm size. The Fort Sill, Okla., bookstore sold these slide rules for $1.50.

This wooden graphical site table has a white coating on both sides. The indicator is clear plastic with wooden edges held together with brass screws. The bottom of the base has a scale marked: Site and Vertical Interval. On one side, the slide has a scale for range and scales for the Target Above Gun (TAG) and Target Below Gun (TBG) with charges of 4 or 5. This side is marked: HOW., 155-MM (/) MI (/) SHELL, M107 (/) FT 155-Q-2. The other side of the slide has another scale for range and TAG/TBG scales for charges of 1, 3, 6, and 7. The back of the instrument has instructions and examples of use. Both sides of the slide, the base, and the back are all marked: 25045.

Compare to 1977.1141.27, whose markings suggest that this instrument was made before 1964. For a graphical firing table, see 2005.0271.02. For Felsenthal company history, see 1977.1141.01 and 1977.1141.02.

This one-sided wooden instrument, similar to a slide rule, was designed in 1964 by Felsenthal Instrument Company but, according to the accession file, made at the Fort Sill Bookstore in Oklahoma. It was used to position a 155 mm howitzer armed with high-explosive M107 shells. The indicator is clear plastic with wooden edges held together with brass screws.

The bottom of the base has a scale labeled Site and Vertical Interval. The lower right corner of the base is marked: Rule 2 (/) Apr 64. On one side, the slide has a scale for range and scales for the Target Above Gun (TAG) and Target Below Gun (TBG) with charges of 5 or 6. The other side of the slide has another scale for range and TAG/TBG scales for charges of 3, 4, and 7. Tables for the observer's position are on the left and right ends of the slide on both sides. Both sides are marked: HOW 155 mm (/) FT 155-AH-1 (/) PROJ, HE, M107 Rule 2 (/) Apr 64.

Tables for angling guns to the left and right at various distances are printed under the slide. The back of the instrument has instructions and examples of use. The markings suggest that this rule was distributed in a white bag. Compare to 1977.1141.26, which may be an earlier version of the instrument.

This ten-inch aluminum linear slide rule is coated with yellow plastic and has a flat nylon indicator. The back of the base has LL1, LL2, A, D, LL3, and LL4 scales, with B, T, ST, S, K, and C scales on the slide. The left end of the slide is marked: MODEL 14 (/) U.S. The right end has the Pickett triangular logo used between 1958 and 1962. The style of the grooved stamped aluminum posts is also consisted with this timeframe.

The top front of the base has scales for "opposite angle" (sine) in both degrees and mils; the top bottom of the base has "Distance D" and A scales. The front of the slide has scales for apex angle (in both mils and degrees), tangent, sine-tangent, sine, and base. The top center of the base is marked: U.S. MILITARY SLIDE RULE.

Pickett & Eckel, Inc., of Chicago and Alhambra, Calif., made this instrument for computations related to the use of field artillery. It fits in an orange-red leather case that has the Pickett logo and US stamped in gold on the front and a metal loop on the back for suspension from a belt. The case is lined with white plastic. A white plastic "data strip" slides into a slot on the case. The strip contains diagrams and equations for trigonometric functions, traverse computations, azimuth and distance from coordinates, triangle computation, and the distance to an artillery target.

The case fits in a brown, black, white, and yellow paper box. The box and its insert are repeatedly marked: ALL METAL SLIDE RULE a rule for every need. The Pickett logo appears between the two segments of the mark. The end of the box once bore a paper tag: 1 UNIT - FSN - 7520 - 656 - 0660 (/) Slide Rule – Military, Field Artillery (/) With Data Strip and Case MIL-S-20195B (/) Mfg. Contr.; PICKETT & ECKEL, INC. Model No. 14.

The object comes from the Felsenthal Collection of computing devices. (See Felsenthal's company history with 1977.1141.02.) Donor Ben Rau suggested a date of 1965 for this slide rule, but it was probably made a few years earlier. Compare to the box collected with 1995.0126.02.

This plastic green and white slide rule carries out calculations related to the capacity, draft, and resistance of cargo tankers able to carry up to 26,700 deadweight metric tons of petroleum or petroleum products. Eight metal rivets hold the rule together. The front is marked: KOEHLER TRIM-NUMERAL CALCULATOR (/) 26700 D.W.T. TANKERS. The bottom of the front of the slide is marked: MARKETED BY JEFKO PRODUCTS COMPANY, 100 OAKLAND ROAD, MAPLEWOOD, NEW JERSEY. The back of the rule and the back of the slide are both marked: COPYRIGHT 1954 BY J. F. KOEHLER.

According to the accession file, this instrument was made by Felsenthal Instrument Company in 1954 as model number FDJ-23. For company history, see 1977.1141.01 and 1977.1141.02. The address for JEFKO Products is a single-family home constructed in 1925. A New Jersey engineer named J. Franklin Koehler (b. 1927) earned a B.S. in naval architecture and marine transportation from the Massachusetts Institute of Technology in 1951 with a thesis titled "Influence of Rising Operating Costs on Relative Economic Operation of Higher Speed Cargo Vessels."

This white plastic circular slide rule consists of a disc riveted to a square backing. The backing has a logarithmic scale of readings of a stadia rod used with a transit telescope, in feet. The disc has two logarithmic scales of angles. The first scale gives the difference in elevation of the transit and the stadia rod, in feet. It represents multiplying the stadia reading by 1/2 sin 2A, where A is the vertical angle of the transit telescope. The second scale finds the horizontal distance of the rod in feet and represents multiplying the stadia reading by the square of cos A. There is no indicator.

The instrument is marked on the front: STADIA COMPUTER. The interior of the disc has DIRECTIONS FOR USE and a table providing the quantity to be added when a constant is used in measuring stadia. On the back, the rule is marked: 6675-664-4676 (/) CONTRACT NO. DSA 700-68-M-AF86 (/) FELSENTHAL INSTRUMENTS CO. (/) CHICAGO, ILLINOIS (/) 22040 (/) MFR'S PART NO. FAE-15. It has a blue plastic case with snaps and a holder for a label. This object was donated with a second, duplicate Felsenthal stadia computer, which was assigned the same catalog number.

The instrument resembles Cox's Stadia Computer (see 1987.0221.01 and 1987.0221.02). Donor Ben Rau dated the object to 1968, which is consistent with the form of the company name on the instrument. For Felsenthal company history, see 1977.1141.01 and 1977.1141.02.

In 1950 and 1951, three Illinois Institute of Technology engineering professors participated in the development of the Versalog slide rule, manufactured by Hemmi of Tokyo, Japan, for the Frederick Post Company of Chicago. E. I. Fiesenheiser, R. A. Budenholzer, and B. A. Fischer subsequently prepared this 115-page hardcover volume explaining the slide rule's capabilities. They covered the care of the instrument, its twenty-three scales, multiplication and division, squares and cubes, exponentials and logarithms, and trigonometric operations. Each professor also contributed a chapter on applications in his specialty: civil, mechanical, or electrical engineering.

This copy is stamped inside the front cover and on the edges: WILLIAM KRUTZ ESQ. See 1978.0800.01.

This 10-inch duplex slide rule is made from a magnesium alloy coated with white celluloid. It has a flat glass indicator with metal sides and stainless steel end posts. One screw on the back bottom side is missing. The top side is engraved with a serial number: CO24920.

The front of the rule has nine D scales, four also labeled 1/N, one also labeled Co, and four also labeled N. The two groups of four scales are extended and folded, so that for reading off logarithms, the rule is the equivalent of a rule 80" long. The slide has CF, CI, and C scales.

The slide has several markings above the scales. The first marking reads: INTERNATIONAL (/) COPYRIGHT 1947 (/) U.S.A. COPYRIGHT 1947 (/) R. C. PICKETT, A. F. ECKEL (/) CHICAGO, U.S.A. Second, there is a table for Digits or Zero for Sine and Tangent and a table for the number of digits in a result found on the C scale. Third, a logo inside an oval reads: DECI• (/) LOG LOG (/) Trade Mark. Fourth is another table for whether a result has zeroes or digits in results for squares, cubes, and roots. The fifth marking reads: THE NUMBER OF ZEROS IS (/) ONE LESS THAN THE ABSO- (/) LUTE VALUE OF THE NEGA- (/) TIVE CHARACTERISTIC. (/) EXAMPLE: 10-5 = .00001. The sixth marking reads: THE NUMBER OF DIGITS IS (/) ONE GREATER THAN THE (/) POSITIVE CHARACTERISTIC. (/) EXAMPLE: 105 = 100,000. Finally, a mark at the right end of the slide reads: PATENTS PENDING (/) MADE IN U.S.A. (/) PICKETT & ECKEL, INC. (/) CHICAGO 3, U.S.A. (/) MODEL 2.

The back of the rule has three cube root scales, an L scale, a D scale, and two square root scales. The scales for roots are folded, so that the rule is the equivalent of 60" in length for cube roots and 20" in length for square roots. The slide has two T scales and ST, S, CI, and C scales. The left side of the slide is marked: INTERNATIONAL (/) COPYRIGHT 1945 (/) U.S.A. COPYRIGHT 1945 (/) R.C. PICKETT, A. F. ECKEL (/) CHICAGO, U.S.A.

Arthur Frederick Eckel (1894–1960) and Roswell Colvert Pickett (1892–1969) partnered in Chicago in 1943 to manufacture slide rules. By 1946, they had transitioned from paper slide rules to magnesium, and Pickett established a branch of the company in Alhambra, Calif. In 1947, Maurice L. Hartung, a University of Chicago professor who helped Pickett & Eckel market their products to schools, described the Model 2 in How to Use the Deci-Log Log Slide Rule (Chicago: Pickett & Eckel, 1947). A copy of this pamphlet is 1979.0601.04. Eckel received four of the patents mentioned as "pending" on the object in 1948 and 1949. He left the company around that time, and his name was removed from slide rules by 1950. Thus, this example was probably made between 1946 and 1950.

Indeed, the donor, Frank M. Graves, reported that he used this rule as a college student. He received a Bachelor of Science degree in chemistry from Syracuse University in 1949.

The rule fits in a brown leather case marked on the flap with "Pickett" in script over a triangular logo. A belt loop on the back of the case is marked: SADDLE (/) LEATHER. The logo was used by the company from 1950 to 1958, so the case may be a replacement. The style of the belt loop, though, differs from the ring construction depicted in Pickett's 1953 catalog. In 1953, Model 2 and its case sold for $21.35.

The citation information for this small 32-page booklet is: Maurice L. Hartung, How to Use the 300 Log Log Trig Pocket Slide Rule (Chicago: Pickett & Eckel, Inc., 1949). It provides general information on how to use slide rules, including the arithmetical operations, locating the decimal point, combining multiplication and division, using the folded scales, calculating roots, trigonometry, and vectors.

Model 300 was a six-inch, pocket-sized duplex slide rule and is not presently represented in the Smithsonian collections, although 1999.0096.01 is a ten-inch log log trig rule. Hartung was a University of Chicago professor who helped Pickett & Eckel market their products to schools and who wrote several instruction manuals for the company's slide rules. See 1979.0601.02.